Envelopes are commonly sealed by wetting or moistening an adhesive material on the flap. Typically, the moistening is accomplished by licking the adhesive. This is not only distasteful but is also likely to leave bacteria on the envelope. Sponges and other devices have been made to provide moisture to the flap. The disadvantage is that effort must be made to wet the envelope to seal it properly.
One alternative envelope is one which uses a pressure sensitive adhesive strip on the inside of the flap with a release tape which covers the adhesive until the envelope is ready for use. The disadvantage of this type of envelope is that a separate release tape must be used. Not only is this more costly to manufacture but it is also cumbersome for the user because the tape has to be pulled off with each use. In addition, the separate tape must be disposed. As is often the case, the separate tape winds up on the floor or as additional garbage to be disposed.